Semiconductor light emitting device and method for manufacturing the same

ABSTRACT

A semiconductor light emitting device includes a first semiconductor layer; a second semiconductor layer on the first semiconductor layer; an active layer on the second semiconductor layer; a third semiconductor layer on the active layer; and a fourth semiconductor layer on the third semiconductor layer, wherein the first semiconductor layer has a composition equation of Al Y (Ga x In 1-x ) 1-Y N(0≦X,Y≦1), wherein the third semiconductor layer has a composition equation of Al Y (Ga x In 1-x ) 1-Y N(0≦X,Y≦1), wherein the active layer includes a plurality of quantum barrier layers and a plurality of quantum well layers having a material different from the quantum barrier layers, wherein the plurality of quantum well layers include an AlGaN based semiconductor layer, wherein the plurality of quantum barrier layers has a larger band gap energy than that of the quantum well layers.

This application is a Continuation of co-pending U.S. patent applicationSer. No. 13/454,650 filed on Apr. 24, 2012, which is a continuation ofU.S. patent application Ser. No. 13/154,133 filed on Jun. 6, 2011, nowU.S. Pat. No. 8,183,555, which is a continuation of U.S. patentapplication Ser. No. 12/982,325 filed on Dec. 30, 2010, now U.S. Pat.No. 8,044,385, which is a continuation of U.S. patent application Ser.No. 12/247,870 filed on Oct. 8, 2008, now U.S. Pat. No. 7,884,350, whichclaims priority under 35 U.S.C. 119 to Korean Patent Application No.10-2007-0100980 filed on Oct. 8, 2007, the entire contents of which arehereby incorporated by reference.

BACKGROUND

The present disclosure relates to a semiconductor light emitting deviceand a method of manufacturing the same.

Groups III-I nitride semiconductors have been variously applied to anoptical device such as blue and green LEDs (Light Emitting Diodes), ahigh speed switching device, such as a MOSFET (Metal Semiconductor FieldEffect Transistor) and an HEMT (Hetero junction Field EffectTransistors), and a light source of a lighting device or a displaydevice.

A nitride semiconductor is mainly used for the LED or an LD (laserdiode), and studies have been continuously conducted to improve themanufacturing process or the light efficiency of the nitridesemiconductor.

SUMMARY

The embodiment provides a semiconductor light emitting device comprisingat least one super lattice layer above and/or below an active layer, anda method of manufacturing the same.

The embodiment provides a semiconductor light emitting device capable ofbuffering stress transferred to an active layer by forming a pluralityof super lattice layers and a plurality of buffer layers below an activelayer, and a method of manufacturing the same.

The embodiment provides a semiconductor light emitting device having asubstantially flat energy band by varying a composition ratio ofmaterials constituting at least a part of an active layer, and a methodof manufacturing the same.

An embodiment provides a semiconductor light emitting device comprising:a first semiconductor layer; a second semiconductor layer on the firstsemiconductor layer; an active layer on the second semiconductor layer;a third semiconductor layer on the active layer; a fourth semiconductorlayer on the third semiconductor layer; a first electrode layerconnected to the first semiconductor layer; a second electrode layerconnected to the fourth semiconductor layer; wherein the firstsemiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the third semiconductorlayer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the active layerincludes a plurality of quantum barrier layers and a plurality ofquantum well layers having a material different from the quantum barrierlayers, wherein the plurality of quantum well layers include an AlGaNbased semiconductor layer, wherein the plurality of quantum barrierlayers has a larger band gap energy than that of the quantum welllayers.

An embodiment provides a semiconductor light emitting device comprising;a first semiconductor layer including an n-type dopant; a secondsemiconductor layer including the n-type dopant on the firstsemiconductor layer; an active layer on the second semiconductor layer,wherein the active layer includes a plurality of quantum barrier layersand a plurality of quantum well layers; a third semiconductor layerincluding a p-type dopant on the active layer; a fourth semiconductorlayer including the p-type dopant on the third semiconductor layer, afirst electrode layer electrically connected to at least one of thefirst and second semiconductor layers; and a second electrode layerelectrically connected to at least one of the third and fourthsemiconductor layers, wherein the first semiconductor layer has acomposition equation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), whereinthe third semiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the active layerincludes a plurality of quantum barrier layers and a plurality ofquantum well layers having a material different from the quantum barrierlayers, wherein the plurality of plurality of quantum well layersinclude an AlGaN based layer, wherein the second electrode layerincludes a reflective layer, wherein the plurality of quantum barrierlayers has a larger band gap energy than that of the quantum welllayers.

An embodiment provides a method of manufacturing a semiconductor lightemitting device comprising; forming a lower super lattice layer, forminga first conductive semiconductor layer on the lower super lattice layer,forming an active layer on the first conductive semiconductor layer,forming a second conductive super lattice layer on the active layer, andforming a second conductive semiconductor layer on the second conductivesuper lattice layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating a semiconductor light emittingdevice according to a first embodiment;

FIG. 2 is a sectional view illustrating a horizontal semiconductor lightemitting device based on the semiconductor light emitting device of FIG.1;

FIG. 3 is a sectional view illustrating a semiconductor light emittingdevice according to a second embodiment;

FIG. 4 is a sectional view illustrating a semiconductor light emittingdevice according to a third embodiment;

FIG. 5 is a sectional view illustrating a semiconductor light emittingdevice according to a fourth embodiment;

FIG. 6 is an energy band diagram of an active layer according to a fifthembodiment;

FIG. 7 is an energy band diagram of an active layer according to a sixthembodiment;

FIG. 8 is an energy band diagram of an active layer according to aseventh embodiment;

FIG. 9 is an energy band diagram of an active layer according to aneighth embodiment;

FIG. 10 is an energy band diagram of an active layer according to aninth embodiment; and

FIG. 11 is an energy band diagram of an active layer according to atenth embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A semiconductor light emitting device and a method for manufacturing thesame according to an embodiment will be described in detail withreference to the accompanying drawings. In the description ofembodiments, it will be understood that when a layer is referred to asbeing ‘on’ or ‘under’ another layer, the reference about ‘on’ and‘under’ each layer will be made on the basis of drawings. Also, thethickness of each layer in the drawings is an example, and is notlimited thereto.

FIG. 1 is a sectional view illustrating a semiconductor light emittingdevice according to a first embodiment.

Referring to FIG. 1, the semiconductor light emitting device 100comprises a substrate 110, a first buffer layer 120, a first superlattice layer 130, a first conductive semiconductor layer 140, an activelayer 150, a second conductive super lattice layer 160 and a secondconductive semiconductor layer 170.

The substrate 110 comprises one selected from the group consisting ofsapphire substrate Al₂O₃, GaN, SiC, ZnO, Si, GaP and GaAs, and may alsobe removed through a physical and/or chemical scheme before or after anelectrode layer is formed.

A nitride semiconductor is grown on the substrate 110 by an E-beamevaporator, a PVD (physical vapor deposition) apparatus, a CVD (chemicalvapor deposition) apparatus, a PLD (plasma laser deposition) apparatus,a dual-type thermal evaporator, a sputtering apparatus, and an MOCVD(metal organic chemical vapor deposition) apparatus. However, the scopeof the present invention is not limited thereto.

The first buffer layer 120 is formed on the substrate 110 to preventstrain caused by lattices or difference of thermal expansioncoefficients between the substrate 110 and an epitaxial layer. A firstconductive dopant may be doped into the first buffer layer 120 or not.The first buffer layer 120 having no first conductive dopant may also beremoved together with the substrate 110.

For example, the first buffer layer 120 satisfies a composition equationof Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) and has a thickness of 10 Å to1000 Å. The first buffer layer 120 is partially polymerized or has asingle crystalline structure. The first buffer layer 120 is grown at thegrowth temperature in the range of 300° C. to 1100° C. and hasresistance in the range of 1×10⁶ Ωcm to 1×10⁻⁴ Ωcm. Further, the firstbuffer layer 120 has one of hexagonal, Wurtzite and Zinc blendstructures.

The first super lattice layer 130 is formed on the first buffer layer120. The first super lattice layer 130 can be formed by alternatelylaminating layers having a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1). The first super lattice layer130 can be formed by alternately laminating compound semiconductorlayers containing at least one of III group elements Al, Ga and In and Vgroup element N. For example, the first super lattice layer 130 isprepared as a pair of GaN/AlInGaN, GaN/InN, and GaN/InN/AlGaN. Aconductive dopant may be doped into the first super lattice layer 130 ornot. The conductive dopant comprises a first conductive dopant and/or asecond conductive dopant.

The first super lattice layer 130 is grown into a super latticestructure by supplying source gas comprising N and at least one of Al,Ga and In at the growth temperature of 500° C. to 1100° C. For example,each layer of the first super lattice layer 130 may have a thickness of5 Å to 100 nm and the first super lattice layer 130 may have 1 to 50pairs of layers and carrier concentration of 10¹⁶/cm³ to 5×10¹⁸/cm³.Further, the first super lattice layer 130 may have one of hexagonal,Wurtzite and Zinc blend structures.

The first super lattice layer 130 attenuates strain. In detail, thestrain transferred through the first buffer layer 120 can be attenuatedby the first super lattice layer 130.

A nitride layer satisfying a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) may be formed between the firstbuffer layer 120 and the first super lattice layer 130.

The first conductive semiconductor layer 140 is formed on the firstsuper lattice layer 130. For example, the first conductive semiconductorlayer 140 comprises semiconductors selected from InAlGaN, GaN, AlGaN,InGaN, AlN and InN that satisfy a composition equation ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). The first conductivedopant is doped into the first conductive semiconductor layer 140. Thefirst conductive dopant comprises Si, Ge, Sn, Se, Te and the like.

The active layer 150 is formed on the first conductive semiconductorlayer 140. The active layer 150 has a single quantum well structure or amulti-quantum well structure. The active layer 150 is selectively formedaccording to a desired wavelength by using N and at least one of Al, Gaand In. Further, the active layer 150 having the multi-quantum wellstructure may have a multi-layer configuration in which the layersconstituting the multi-layer configuration may have the same compositionor different compositions, and may have a thickness of 5 nm to 40 nmwith an arrangement of a quantum well layer (not shown) and a quantumbarrier layer (not shown).

The second conductive super lattice layer 160 is formed on the activelayer 150. The second conductive super lattice layer 160 is doped withsecond conductive dopant. The second conductive super lattice layer 160can be formed by alternately laminating layers having a compositionequation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1). The secondconductive super lattice layer 160 comprises 1 to 30 pairs of layersgrown at the predetermined growth temperature. For example, each layerof the second conductive super lattice layer 160 may have a thickness of5 Å to 100 nm.

The second conductive super lattice layer 160 has carrier concentrationof 10¹⁶/cm³ to 5×10²²/cm³ and resistance of 1×10⁻⁴ Ωcm to 1×10¹² Ωcm.The second conductive super lattice layer 160 may have one of hexagonal,Wurtzite and Zinc blend structures.

Each pair of the first super lattice layer 130 and the second conductivesuper lattice layer 160 may have doping concentration, thickness andcomposition equation which may vary depending on application.

The second conductive semiconductor layer 170 is formed on the secondconductive super lattice layer 160. The second conductive semiconductorlayer 170 is doped with the second conductive dopant and comprisessemiconductors selected from InAlGaN, GaN, AlGaN, InGaN, AlN and InNthat satisfy a composition equation of In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1,0≦y≦1, 0≦x+y≦1). A third conductive semiconductor layer (not shown)and/or a transparent electrode layer (not shown) may be formed on thesecond conductive semiconductor layer 170.

If the first conductive semiconductor layer 140 is an N typesemiconductor layer, the third conductive semiconductor layer isprepared in the form of an N type semiconductor layer. However, if thefirst conductive semiconductor layer 140 is a P type semiconductorlayer, the third conductive semiconductor layer is prepared in the formof a P type semiconductor layer. Thus, the semiconductor light emittingdevice 100 may comprise at least one of N-P, P-N, N-P-N and P-N-Pjunction structures.

FIG. 2 is a sectional view illustrating a horizontal semiconductor lightemitting device based on the semiconductor light emitting device ofFIG. 1. In the following description of FIG. 2, the elements that havebeen described with reference to FIG. 1 will be denoted with the samereference numerals, and the detailed description thereof will beomitted.

Referring to FIG. 2, the semiconductor light emitting device 101comprises a first electrode layer 181 formed on the first conductivesemiconductor layer 140, and a second electrode layer 183 formed on thesecond conductive semiconductor layer 170.

Further, the embodiment can provide a vertical semiconductor lightemitting device based on the semiconductor light emitting device ofFIG. 1. For example, in the semiconductor light emitting device of FIG.1, a reflective electrode layer (not shown) and a conductive supportsubstrate (not shown) are formed on the second conductive semiconductorlayer 170. The substrate 110, the first buffer layer 120 and the firstsuper lattice layer 130 are removed using physical and/or chemicaletching, and a first electrode layer is formed below the firstconductive semiconductor layer 140. The first buffer layer 120 or thefirst super lattice layer 130 may not be removed if the first bufferlayer 120 or the first super lattice layer 130 has specific conductiveproperty.

FIG. 3 is a sectional view illustrating a semiconductor light emittingdevice according to a second embodiment. In the following description ofFIG. 3, the same elements that have been described with reference to thefirst embodiment will be denoted with the same reference numerals, andthe detailed description thereof will be omitted.

Referring to FIG. 3, the semiconductor light emitting device 100Acomprises a substrate 110, a first buffer layer 120, a first superlattice layer 130, a first nitride layer 131, a second super latticelayer 135, a first conductive semiconductor layer 140, an active layer150, a second conductive super lattice layer 160 and a second conductivesemiconductor layer 170.

According to the second embodiment, the super lattice layers 130 and 135are formed below the first conductive semiconductor layer 140 or theactive layer 150 while being spaced apart from each other. The growthconditions and composition materials of the super lattice layers 130 and135 may be identical to or different from each other.

The first super lattice layer 130 can be formed on the first bufferlayer 120 by alternately laminating layers having a composition equationof Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), and may be doped with a firstconductive dopant. For example, the first super lattice layer 130 mayhave 1 to 50 pairs of layers, and each layer of the first super latticelayer 130 may have a thickness of about 5 Å to 100 nm. The first superlattice layer 130 is grown at the temperature of 500˜1100° C. and hascarrier concentration of 10¹⁶/cm³ to 5×10¹⁸/cm³. Further, the firstsuper lattice layer 130 has one of hexagonal, Wurtzite and Zinc blendstructures.

The first super lattice layer 130 primarily attenuates strain. Indetail, the strain transferred through the first buffer layer 120 can beattenuated by the first super lattice layer 130.

A layer having a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) may be formed between the firstbuffer layer 120 and the first super lattice layer 130. However, thescope of the present invention is not limited thereto.

The first nitride layer 131 is formed on the first super lattice layer130. The first nitride layer 131 has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), and may be doped with the firstconductive dopant. For example, the first nitride layer 131 may have athickness of 0.001 um to 3 um at the growth temperature is 500° C. to1200° C. The first nitride layer 131 may have carrier concentration of10¹⁵/cm³ to 10²⁰/cm³ and resistance of 1×10⁴ Ωcm to 1×10⁻⁴ Ωcm. Thefirst nitride layer 131 may have one of hexagonal, Wurtzite and Zincblend structures. The first nitride layer 131 can improve the quality ofthe semiconductor layer on the first super lattice layer 130.

The second super lattice layer 135 is formed on the first nitride layer131. The second super lattice layer 135 can be formed by alternatelylaminating layers having a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X≦1,0<Y≦0.4) and may be doped with thefirst conductive dopant. The second super lattice layer 135 comprises apredetermined number of material layers having a super lattice structureand the material layers form a predetermined number (e.g. 1 to 50) ofpairs. For example, each layer of the second super lattice layer 135 mayhave a thickness of about 10 Å˜500 nm at the growth temperature is 500°C. to 1100° C. The second super lattice layer 135 may have carrierconcentration is 10¹⁷/cm³ to 8×10²⁰/cm³. The second super lattice layer135 may have one of hexagonal, Wurtzite and Zinc blend structures.

One pair of the second super lattice layer 135 comprises layers havingcompositions different from each other or having the same composition,and each pair may comprise one to three layers.

The composition and doping concentration of the conductive dopant forthe first and second super lattice layers 130 and 135 may be identicalto or different from each other.

The first conductive semiconductor layer 140 is formed on the secondsuper lattice layer 135, the active layer 150 is formed on the firstconductive semiconductor layer 140, the second conductive super latticelayer 160 is formed on the active layer 150, and the second conductivesemiconductor layer 170 is formed on the second conductive super latticelayer 160. Further, a third conductive semiconductor layer (not shown)and/or a transparent electrode layer (not shown) may be formed on thesecond conductive semiconductor layer 170.

The semiconductor light emitting device according to the secondembodiment can be prepared in the form of a horizontal or vertical lightemitting device, and can be formed with at least one of N-P, P-N, N-P-Nand P-N-P junction structures.

According to the second embodiment, the super lattice layers 130 and 135are disposed between the substrate 110 and the first conductivesemiconductor layer 140, so that strain transferred from the substrate110 can be reduced step by step. For example, the first super latticelayer 130 primarily reduces the strain which is not reduced by the firstbuffer layer 120, and the second super lattice layer 135 secondarilyreduces the remaining strain, so that ESD (electro-static discharge)properties of the active layer 150 can be improved.

FIG. 4 is a sectional view illustrating a semiconductor light emittingdevice according to a third embodiment. In the following description ofFIG. 4, the same elements that have been described with reference to thefirst and second embodiments will be denoted with the same referencenumerals, and the detailed description thereof will be omitted.

Referring to FIG. 4, the semiconductor light emitting device 100Bcomprises plural super lattice layers 130 and 135 and plural bufferlayers 120 and 132 formed below a first conductive semiconductor layer140.

The semiconductor light emitting device 100B comprises a substrate 110,a first buffer layer 120, a first super lattice layer 130, a firstnitride layer 131, a second buffer layer 132, a second super latticelayer 135, a first conductive semiconductor layer 140, a firstconductive nitride layer 145, an active layer 150, a second conductivesuper lattice layer 160, a second conductive nitride layer 162 and asecond conductive semiconductor layer 170.

The first super lattice layer 130 is formed on the first buffer layer120, the first nitride layer 131 is formed on the first super latticelayer 130, the second buffer layer 132 is formed on the first nitridelayer 131, and the second super lattice layer 135 is formed on thesecond buffer layer 132. The first and second buffer layers 120 and 132may have the same physical and chemical properties. In the structure ofthe semiconductor light emitting device 100B, the substrate 110, thefirst buffer layer 120, the first super lattice layer 130, the firstnitride layer 131 and the second buffer layer 132 may be removed beforeor after an electrode layer is formed.

The second buffer layer 132 secondarily prevents defect generated fromthe layers below the second buffer layer 132.

For example, the second buffer layer 132 may have a thickness of 0.0001um to 0.1 um at the growth temperature of 400° C. to 1200° C. At thistime, the second buffer layer 132 prevents threading dislocationtransferred from the substrate 110 through semiconductor layers. Thesecond buffer layer 132 may have the material composition ratio orgrowth temperature different from that of the first buffer layer 120.

The first conductive nitride layer 145 is formed on the first conductivesemiconductor layer 140. The first conductive nitride layer 145 has acomposition equation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) and mayhave a thickness of 0.0001 um to 0.5 um at the growth temperature of700° C. to 950° C.

The second conductive nitride layer 162 is formed on the secondconductive super lattice layer 160 and the second conductivesemiconductor layer 170 is formed on the second conductive nitride layer162.

A second conductive dopant is doped into the second conductive nitridelayer 162 satisfying a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1). The second conductive nitridelayer 162 has carrier concentration of 10¹⁶/cm³ to 10²²/cm³, resistanceof 10⁻⁴ Ωcm to 10¹² Ωcm and thickness of 5 nm to 100 nm. Further, thesecond conductive nitride layer 162 may have one of hexagonal, Wurtziteand Zinc blend structures.

The semiconductor light emitting device according to the thirdembodiment can be prepared in the form of a horizontal or vertical lightemitting device, and can be formed with at least one of N-P, P-N, N-P-Nand P-N-P junction structures.

According to the third embodiment, the super lattice layers 130 and 135and the buffer layers 120 and 132 are formed below the active layer 150,so that strain transferred to the active layer 150 can be minimized.

FIG. 5 is a sectional view illustrating a semiconductor light emittingdevice according to a fourth embodiment. In the following description ofFIG. 5, the same elements that have been described with reference to thefirst to third embodiments will be denoted with the same referencenumerals, and the detailed description thereof will be omitted.

Referring to FIG. 5, the semiconductor light emitting device 100Ccomprises a substrate 110, a first buffer layer 120, a first superlattice layer 130, a first nitride layer 131, a second buffer layer 132,a second nitride layer 133, a second super lattice layer 135, a firstconductive semiconductor layer 140, a third super lattice layer 141, afirst-A conductive semiconductor layer 142, a first conductive nitridelayer 145, an active layer 150, a second conductive super lattice layer160, a second conductive nitride layer 162 and a second conductivesemiconductor layer 170.

The substrate 110, the first buffer layer 120, the first super latticelayer 130, the first nitride layer 131, the second buffer layer 132, thesecond nitride layer 133 and the second super lattice layer 135 aresequentially formed below the first conductive semiconductor layer 140.

The first nitride layer 131, the second buffer layer 132 and the secondnitride layer 133 are sequentially formed between the first superlattice layer 130 and the second super lattice layer 135.

The first nitride layer 131 satisfies a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) and may be doped with a firstconductive dopant. For example, the first nitride layer 131 may have athickness of 0.001 um to 3 um at the growth temperature of 500° C. to1200° C. The first nitride layer 131 may have carrier concentration of10¹⁵/cm³ to 10²⁰/cm³ and resistance of 1×10⁴ Ωcm to 1×10⁻⁴ Ωcm. Further,the first nitride layer 131 may have one of hexagonal, Wurtzite and Zincblend structures. The first nitride layer 131 can improve the quality ofthe semiconductor layer on the first super lattice layer 130.

The second nitride layer 133 satisfying a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) is formed on the second bufferlayer 132. For example, the second nitride layer 133 may have athickness of 0.001 um to 3 um at the growth temperature of 500° C. to1200° C. The second nitride layer 133 may be doped with a firstconductive dopant and may have one of hexagonal, Wurtzite and Zinc blendstructures. The second nitride layer 133 can improve the quality of thesemiconductor layer.

The third super lattice layer 141 is formed on the first conductivesemiconductor layer 140. The third super lattice layer 141 can be formedby alternately laminating layers having a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0<Y<0.25, 0≦X≦1). Each layer of the thirdsuper lattice layer 141 may have a thickness of 10 Å to 500 nm and mayhave one of hexagonal, Wurtzite and Zinc blend structures.

The first-A conductive semiconductor layer 142 is formed on the thirdsuper lattice layer 141. For example, the first-A conductivesemiconductor layer 142 comprises semiconductor materials selected fromInAlGaN, GaN, AlGaN, InGaN, AlN and InN that satisfy a compositionequation of In_(x)Al_(Y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). The first-Aconductive semiconductor layer 142 may be doped with the firstconductive dopant and may have carrier concentration of 10¹⁶/cm³ to10²⁰/cm³.

The semiconductor light emitting device 100C according to the fourthembodiment can be prepared in the form of a horizontal semiconductorlight emitting device by performing Mesa etching, or a verticalsemiconductor light emitting device after a reflective electrode layerand a conductive support substrate are formed and then the substrate isremoved. However, the scope of the present invention is not limitedthereto.

According to the fourth embodiment, three or more super lattice layers130, 135 and 141 are formed below the active layer 150, so thatinterlayer stress can be reduced. Further, the first buffer layer 120 isformed below the first super lattice layer 130 and the second bufferlayer 132 is formed below the second super lattice layer 135, so thatstrain transferred from the substrate 110 can be reduced. Thus, thestrain transferred to the active layer 150 can be reduced step by stepand ESD properties of the active layer 150 can be improved.

Meanwhile, the active layer 150 according to the first to fourthembodiments comprises a single quantum well structure or a multi-quantumwell structure. The active layer 150 can be formed by alternatelylaminating a quantum well layer (not shown) and a quantum barrier layer(not shown) at a predetermined cycle of 2 to 10. However, the scope ofthe present invention is not limited thereto.

Further, the quantum well layer of the active layer 150, for example,may comprise InGaN or InAlGaN. The quantum barrier layer, for example,may comprise AlGaN or InAlGaN. Further, the quantum barrier layer maycomprise GaN.

The active layer 150 comprises materials having band gap energyaccording to wavelength of emitted light. For example, the quantum welllayer and the quantum barrier layer can be formed with a cycle ofInGaN/GaN, a cycle of InGaN/AlGaN, or a cycle of InAlGaN/InAlGaN.Further, the active layer 150 may comprise materials emitting chromaticlight such as orange light, yellow light, purple light, ultravioletlight, light having a red wavelength, and light having a greenwavelength.

For example, in order to form the active layer 150, source gas, such asNH₃, TMGa (or TEGa) and TMIn, is selectively supplied by using carriergas, such as H₂ and/or N₂, at the predetermined growth temperature (e.g.700° C. to 950° C.), thereby forming the quantum well layer comprisingInGaN and the quantum barrier layer comprising GaN. When the quantumbarrier layer comprises AlGaN, the quantum barrier is formed bysupplying TMAl as source gas.

In the quantum well layer containing indium, a composition ratio ofindium can be reduced step by step. In the quantum barrier layercontaining AlGaN, a composition ratio of aluminum is reduced step bystep. Further, the quantum well layer, in which the composition ratio ofindium has been changed, can be applied to at least one layer or alllayers. Further, the quantum barrier layer, in which the compositionratio of aluminum has been changed, can be applied to at least one layeror all layers.

Each quantum well layer has a thickness of 15 Å to 30 Å and each quantumbarrier layer has a thickness of 50 Å to 300 Å. However, the scope ofthe present invention is not limited thereto.

Meanwhile, the active layers 150 disclosed in the first to fourthembodiments comprise characteristics of one active layer disclosed inembodiments of FIGS. 6 to 11.

Further, the technical features of the first to fourth embodiments canbe applied to other embodiments.

FIGS. 6 to 11 are energy band diagrams of an active layer according tofifth to eleventh embodiments. Hereinafter, for convenience indescription, a first conductive type semiconductor layer will bereferred to as an n-type semiconductor layer or an n-side, a secondconductive type semiconductor layer will be referred to as a p-typesemiconductor layer or a p-side.

FIG. 6 is an energy band diagram of an active layer according to a fifthembodiment. FIG. 6A is a band diagram of an active layer designed inanticipation of a stress of a quantum well layer, and FIG. 6B is a banddiagram after growing the active layer designed as illustrated in FIG.6A.

Referring to FIG. 6A, a band diagram of a quantum well layer 43A isdesigned in anticipation of a quantum well layer 42 (dot line) to bedeformed due to a stress as illustrated in FIG. 6B. That is, an energyband potential of the quantum well layer 43A is designed so that ann-type semiconductor layer side is low, and a p-type semiconductor layerside is high. Here, the energy band of the quantum well layer 43A may bedesigned so that the energy band potential of the n-type semiconductorlayer side is lower than a reference potential, and the energy bandpotential of the p-type semiconductor layer side is equal to thereference potential.

A quantum barrier layer 53A is designed with a flat energy band.

Referring to FIG. 6B, an active layer is grown according to the banddiagram designed as illustrated in FIG. 6A. In initial growth, a quantumwell layer 43 of the active layer has a relatively high In content, andthereafter, the In content is reduced in a graded manner up to areference amount during the growth. As a result, the quantum well layer43 can have an energy band (or an approximately flat band) havinguniform band gap. That is, in an energy band potential of the quantumwell layer 43, the energy band potential of the n-type semiconductorlayer side is equal to that of the p-type semiconductor layer side.

Each quantum well layer 43 is grown by changingIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N (0<a≦1, 0<a1≦1, b=1-a, b1=1-a1, a>a1)according to a growth time.

An In composition ratio of the InGaN quantum well layer 43 can bereduced in a graded manner to compensate an energy deformation due to astress generated at a boundary between the InGaN quantum well layer 43and the GaN or AlGaN quantum barrier layer 53A. Also, the quantum welllayer 43 the approximately flat energy band or the uniform band gap canbe applied to at least one layer or all layers of the quantum well layer43.

A stress is applied to an energy band potential of a quantum barrierlayer 53 so that the energy band potential of the n-type semiconductorlayer side is low, and the energy band potential of the p-typesemiconductor layer side is high.

FIG. 7 is an energy band diagram of an active layer according to a sixthembodiment. FIG. 7A is a band diagram of an active layer designed inanticipation of a stress of a quantum barrier layer, and FIG. 7B is aband diagram after growing the active layer designed as illustrated inFIG. 7A.

Referring to FIG. 7A, a band diagram of a quantum barrier layer 54A isdesigned in anticipation of a quantum barrier layer (See referencenumeral 52 of FIG. 7B) to be deformed due to a stress. That is, anenergy band potential of the quantum barrier layer 54A is designed sothat an n-type semiconductor layer side is high, and a p-typesemiconductor layer side is low. A quantum well layer 44A is designedwith a flat energy band.

Here, the energy band of the quantum barrier layer 54A may be designedso that the energy band potential of the n-type semiconductor layer sideis higher than a reference potential, and the energy band potential ofthe p-type semiconductor layer side is equal to the reference potential.

Referring to FIG. 7B, an active layer is grown according to the banddiagram designed as illustrated in FIG. 7A. In initial growth, a quantumbarrier layer 54 of the active layer has a relatively high Al content,and thereafter, the Al content is reduced in a graded manner up to areference amount during the growth. As a result, the quantum barrierlayer 54 can have the approximately flat energy band or the uniform bandgap.

A stress is applied to an energy band potential of a quantum well layer44 so that the energy band potential of the n-type semiconductor layerside is high, and the energy band potential of the p-type semiconductorlayer side is low.

The quantum well layer 44 is formed of InGaN. The quantum barrier layer54 can be grown by changing Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N (0<c≦1,0<c1≦1, d=1-c, d1=1-c1, c>c1) according to a growth time.

An Al composition ratio may be reduced in a graded manner according tothe growth time to form the AlGaN barrier layer 54. Also, a cycle ofAl_(c)Ga_(d)N/Al_(c1)Ga_(d1)N may be repeated to form the quantumbarrier layer 54. Bending of the energy band due to the stress can becompensated in the quantum barrier layer 54.

Also, the quantum barrier layer 54 having an approximately flat energyband can be applied to at least one layer or all layers of the quantumbarrier layer 54.

FIG. 8 is an energy band diagram of an active layer according to aseventh embodiment. FIG. 8A is a band diagram of an active layerdesigned in anticipation of stresses of a quantum well layer and aquantum barrier layer, and FIG. 8B is a band diagram after growing theactive layer designed as illustrated in FIG. 8A.

Referring to FIG. 8A, a quantum well layer 45A and a quantum barrierlayer 55A of an active layer are designed in anticipation of adeformation of an energy band due to a stress. The quantum well layer45A is formed of InGaN. An energy band potential of the quantum welllayer 45A is designed so that the energy band potential of an n-typesemiconductor layer side is lower than that of a p-type semiconductorlayer side. The quantum barrier layer 55A is formed of AlGaN. An energyband potential of the quantum barrier layer 55A is designed so that theenergy band potential of an n-type semiconductor layer side is higherthan that of a p-type semiconductor layer side. That is, the energy bandpotential of the quantum well layer 45A is designed so that the n-typesemiconductor layer side is low with respect to the p-type semiconductorlayer side. The energy band potential of the quantum barrier layer 55Ais designed so that the n-type semiconductor layer side is high withrespect to the p-type semiconductor layer side.

In the design of the energy band of the quantum well layer 45A and/orthe quantum barrier layer 55A, although the p-type semiconductor layerside is designed as a reference potential, but it is one example. Forexample, a middle portion of the quantum well layer 45A or the quantumbarrier layer 55A or the n-type semiconductor layer side is designed asthe reference potential.

Referring to FIG. 8B, an active layer is grown according to the banddiagram designed as illustrated in FIG. 8A. In initial growth, a quantumwell layer 45 of the active layer has a relatively high In content, andthereafter, the In content is reduced in a graded manner up to areference amount during the growth. As a result, the quantum well layer45 can have the approximately flat energy band or the uniform band gap.That is, in the energy band of each quantum well layer 45, the energyband potential of the n-type semiconductor layer side is equal to thatof the p-type semiconductor layer side.

The quantum well layer 45 is grown by changingIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N (0<a≦1, 0<a1≦1, b=1-a, b1=1-a1, a>a1)according to a growth time.

An In composition ratio of the InGaN quantum well layer 45 can bereduced in a graded manner to compensate an energy deformation due to astress generated at a boundary between the InGaN quantum well layer 45and the AlGaN quantum barrier layer 55. Also, the quantum well layer 45having the approximately flat energy band or the uniform band gap can beapplied to at least one layer or all layers of the quantum well layer43.

In initial growth, a quantum barrier layer 55 of the active layer has arelatively high Al content, and thereafter, the Al content is reduced ina graded manner up to a reference amount during the growth. As a result,the quantum barrier layer 55 can have the approximately flat energy bandor the uniform band gap.

The quantum barrier layer 55 can be grown by changingAl_(c)Ga_(d)N/Al_(c1)Ga_(d3)N (0<c≦1, 0<c1≦1, d=1-c, d1=1-c1, c>c1)according to a growth time. An Al composition ratio may be reduced in agraded manner according to the growth time to form the AlGaN barrierlayer 55. Also, a cycle of Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N may be repeatedto form the quantum barrier layer 55. Bending of the energy band due tothe stress can be compensated in the quantum barrier layer 55. Also, thequantum barrier layer 55 having the approximately flat energy band orthe uniform band gap can be applied to at least one layer or all layersof the quantum barrier layer 55.

The seventh embodiment can compensate the deformation of the energy banddue to the stress in at least one cycle or all cycles comprising thecycle of the quantum barrier layer 55 and the quantum well layer 45 ofthe active layer.

FIG. 9 is an energy band diagram of an active layer according to aneighth embodiment. The eighth embodiment will compensate a deformationof an energy band using a quantum well layer having a super latticestructure. FIG. 9A is a band diagram of an active layer designed inanticipation of stresses of a quantum well layer, and FIG. 9B is a banddiagram after growing the active layer designed as illustrated in FIG.9A.

Referring to FIG. 9A, a quantum well layer 46A of an active layer has asuper lattice structure 46B. At least one layer or all layers of thequantum well layer 46A may have the super lattice structure 46B, but thepresent disclosure is not limited thereto.

An n-type semiconductor layer side of the quantum well layer 46A isgrown in the super lattice structure 46B and in one cycle or more, and ap-type semiconductor layer side is grown in the super lattice structure46B or a normal condition. The super lattice structure 46B of thequantum well layer 46A may be formed of In_(a)Ga_(b)N/In_(a1)Ga_(b1)N(0<a≦1, 0<a1≦1, b=1-a, b1=1-a1, a1, a>a1).

The super lattice structure 46B of the quantum well layer 46A is grownin order of from a material having a small band gap to a material havinga large band gap. Here, the material having the large band gap is amaterial having a low In content, and the material having the small bandgap is a material having high In content.

A quantum barrier layer 56A of the active layer may be formed of AlGaNor GaN and be designed with a flat energy band potential.

Referring to FIG. 9B, an active layer is grown according to the banddiagram designed as illustrated in FIG. 9A. In initial growth, a quantumwell layer 46 of the active layer may be grown in a cycle of anIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N super lattice structure (See referencenumeral 46B of FIG. 9A) and in one cycle or more, and thereafter, may begrown in the normal condition or the above-described super latticestructure. The In_(a)Ga_(b)N/In_(a1)Ga_(b1)N super lattice structure isgrown in order of from the material having the small band gap to thematerial having the large band gap. That is, theIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N super lattice structure is grown in orderof In_(a)Ga_(b)N and In_(a1)Ga_(b1)N (0<a1≦a≦1).

In the InGaN quantum well layer 46A, a deformation of the energy band ofthe quantum well layer 46 can be compensated using a characteristic inwhich a band gap is changed according to the In content.

The quantum well layer 46 can have the approximately flat energy band orthe uniform band gap because the deformation of the energy band thereofcan be compensated.

The active layer according to the eighth embodiment may comprise thequantum well layer 46 having the super lattice structure and selectivelycomprise the quantum well layer as described in the fifth embodimentand/or the quantum barrier layer as described in the sixth embodiment.

FIG. 10 is an energy band diagram of an active layer according to aninth embodiment. The ninth embodiment will compensate a deformation ofan energy band using a quantum barrier layer having a super latticestructure. FIG. 10A is a band diagram of an active layer designed inanticipation of stresses of a quantum barrier layer, and FIG. 10B is aband diagram after growing the active layer designed as illustrated inFIG. 10A.

Referring to FIG. 10A, a quantum barrier layer 57A of an active layerhas a super lattice structure 57B. At least one layer or all layers ofthe quantum barrier layer 57A may have the super lattice structure 57B,but the present disclosure is not limited thereto.

An n-type semiconductor layer side of the quantum barrier layer 57A isgrown in the super lattice structure 57B and in one cycle or more, and ap-type semiconductor layer side is grown in the super lattice structure57B or a normal condition. Here, super lattice structure 57B is grown ina cycle of Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N (0<c≦1, 0<c1≦1, d=1-c, d1=1-c1,c>c1).

The super lattice structure 57B of the quantum barrier layer 57A may begrown in order of from a material having a large band gap to a materialhaving a small band gap. Here, the material having the large band gap isa material having a high Al content, and the material having the smallband gap is a material having low Al content.

Referring to FIG. 10B, an active layer is grown according to the banddiagram designed as illustrated in FIG. 10A. In initial growth, aquantum barrier layer 57 of the active layer may be grown in a cycle ofan Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N super lattice structure and in onecycle or more, and thereafter, may be grown in the normal condition orthe above-described super lattice structure. TheAl_(c)Ga_(d)N/Al_(c1)Ga_(d1)N super lattice structure of the quantumbarrier layer 57 is grown in order of from the material having the largeband gap to the material having the small band gap. That is, theAl_(c)Ga_(d)N/Al_(c1)Ga_(d1)N super lattice structure is grown in orderof Al_(c)Ga_(d)N having the large band gap and Al_(c1)Ga_(d1)N havingthe small band gap (c>c1).

As a result, the quantum barrier layer 57 can have an approximately flatenergy band or the uniform band gap because the deformation of theenergy band thereof can be compensated. The deformation of the energyband due to the stress can be prevented or minimized in the quantumbarrier layer 57.

FIG. 11 is an energy band diagram of an active layer according to atenth embodiment. The tenth embodiment will compensate a deformation ofan energy band using a quantum well layer and a quantum barrier layer ofa super lattice structure. FIG. 11A is a band diagram of an active layerdesigned in anticipation of stresses of a quantum well layer and aquantum barrier layer, and FIG. 11B is a band diagram after growing theactive layer designed as illustrated in FIG. 11A.

Referring to FIG. 11A, a quantum well layer 48A of an active layer maybe grown in a first super lattice structure 48B in a partial region orall region. The quantum barrier layer 58A may be grown in a second superlattice structure 58B in a partial region or all regions. The first andsecond super lattice structures 48B and 58B may be grown in one cycle ormore.

The first super lattice structure 48B comprises anIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N super lattice structure, and the secondlattice structure 58B comprises an Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N superlattice structure.

The first super lattice structure 48B of the quantum well layer 48A isdisposed toward an n-type semiconductor layer, and a p-typesemiconductor layer side is grown in the first super lattice structure48B or a normal condition. The second super lattice structure 58B of thequantum barrier layer 58A is disposed toward the n-type semiconductorlayer, and the p-type semiconductor side is grown in the second superlattice structure 58B or the normal condition.

The first super lattice structure 48B of the quantum well layer 48A maybe grown in order of from a material having a small band gap to amaterial having a large band gap. The second super lattice structure 58Bof the quantum barrier layer 58A may be grown in order of from thematerial having the large band gap to the material having the small bandgap. Here, as an In content increases, the band gap decreases, and asthe In content decreases, the band gap increases.

Referring to FIG. 11B, in initial growth, a quantum well layer 48 of theactive layer may be grown in a cycle of In_(a)Ga_(b)N/In_(a1)Ga_(b1)N ofthe first super lattice structure (See reference numeral 48B of FIG.11A) and in one cycle or more, and thereafter, may be grown in thenormal condition or the first super lattice structure. TheIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N super lattice structure of the quantumwell layer 48 is grown in order of from the material having the smallband gap to the material having the large band gap. That is, theIn_(a)Ga_(b)N/In_(a1)Ga_(b1)N super lattice structure is grown in orderof from In_(a)Ga_(b)N (0<a1<a≦1) to In_(a1)Ga_(b1)N (0<a1<a≦1).

In the InGaN quantum well layer 48, a deformation of the energy band ofthe quantum well layer 48 can be compensated using a characteristic inwhich a band gap is changed according to the In content.

The quantum well layer 48 can have the approximately flat energy band orthe uniform band gap because the deformation of the energy band thereofcan be compensated.

Also, in initial growth, a quantum barrier layer 58 of the active layermay be grown in a cycle of Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N of the secondsuper lattice structure and in one cycle or more, and thereafter, may begrown in the normal condition or the above-described super latticestructure. The Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N super lattice structure ofthe quantum barrier layer 58 is grown in order of from the materialhaving the large band gap to the material having the small band gap.That is, the Al_(c)Ga_(d)N/Al_(c1)Ga_(d1)N super lattice structure isgrown in order of from Al_(c)Ga_(d)N (0≦c1<c≦1) having the large bandgap to Al_(c1)Ga_(d1)N (0≦c1<c≦1) having the small band gap. Here, inthe AlGaN quantum barrier layer 58, the material having the large bandgap is a material having a high Al content, and the material having thesmall band gap is a material having low Al content.

As a result, the quantum barrier layer 58 can have the approximatelyflat energy band or the uniform band gap because the deformation of theenergy band thereof can be compensated. The deformation of the energyband due to the stress can be prevented or minimized in the quantumbarrier layer 58.

In the fifth to tenth embodiments, a composition ratio of at least oneof In, Al, and Ga is adjusted in at least one layer or all layers of thequantum well layer and/or the quantum barrier layer of the active layerto previously deform the energy band, thereby providing an approximatelyflat energy band to the quantum well layer and/or the quantum barrierlayer even if the energy band deformation occurs due to the stress.

Also, by preventing the piezoelectric field due to the stress from beinggenerated in the active layer, electrons and holes are gathered in amiddle of the quantum well to evaluate probability for generation ofpairs of electrons and holes, thereby improving the luminous efficiency.In addition, reduction of the internal luminous efficiency can beprevented, and light having a wavelength corresponding to a proper bandgap can be emitted.

Although a compound semiconductor light emitting device comprising a N-Pjunction structure is used in the embodiments, the present disclosure isnot limited thereto. For example, a compound semiconductor lightemitting device comprising N-P-N, P-N, P-N-P junction structures may beused.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is comprised in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A semiconductor light emitting device,comprising: a first semiconductor layer; a second semiconductor layer onthe first semiconductor layer; an active layer on the secondsemiconductor layer; a third semiconductor layer on the active layer; afourth semiconductor layer on the third semiconductor layer; a firstelectrode layer connected to the first semiconductor layer; and a secondelectrode layer connected to the fourth semiconductor layer; wherein thefirst semiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the third semiconductorlayer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the active layerincludes a plurality of quantum barrier layers and a plurality ofquantum well layers having a material different from the quantum barrierlayers, wherein the plurality of quantum barrier layers has a largerband gap energy than that of the quantum well layers, wherein the secondsemiconductor layer has a thickness range of 1 nm to 500 nm and has athickness thicker than that of the third semiconductor layer, andwherein the plurality of quantum well layers of the active layerincludes an InAlGaN semiconductor layer.
 2. The semiconductor lightemitting device according to claim 1, wherein the second semiconductorlayer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X≦1,0<Y≦0.4).
 3. The semiconductor lightemitting device according to claim 1, wherein the second semiconductorlayer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0<Y<0.25, 0≦X≦1).
 4. The semiconductorlight emitting device according to claim 1, wherein the secondsemiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1) and has a thickness a thinnerthan that of the first semiconductor layer.
 5. The semiconductor lightemitting device according to claim 1, wherein the first and secondsemiconductor layers include an AlGaN based layer and are formed in ann-type semiconductor layer.
 6. The semiconductor light emitting deviceaccording to claim 5, wherein the first semiconductor layer has athickness thicker than that of the fourth semiconductor layer and thethird semiconductor layer has a thickness thinner than that of thefourth semiconductor layer.
 7. The semiconductor light emitting deviceaccording to claim 6, wherein the first semiconductor layer has athickness range of 0.001 μm to 3 μm.
 8. The semiconductor light emittingdevice according to claim 1, wherein the fourth semiconductor layer hasa composition equation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1).
 9. Thesemiconductor light emitting device according to claim 1, wherein thefourth semiconductor layer has a composition equation ofIn_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1) and has a thicknessdifferent from the third semiconductor layer.
 10. The semiconductorlight emitting device according to claim 1, wherein the fourthsemiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1).
 11. The semiconductor lightemitting device according to claim 5, wherein the third and fourthsemiconductor layers have an AlGaN based layer and are formed in ap-type semiconductor layer.
 12. A semiconductor light emitting device,comprising: a first semiconductor layer including an n-type dopant; asecond semiconductor layer including the n-type dopant on the firstsemiconductor layer; an active layer on the second semiconductor layer,wherein the active layer includes a plurality of quantum barrier layersand a plurality of quantum well layers; a third semiconductor layerincluding a p-type dopant on the active layer; a fourth semiconductorlayer including the p-type dopant on the third semiconductor layer, afirst electrode layer electrically connected to at least one of thefirst and second semiconductor layers; and a second electrode layerelectrically connected to at least one of the third and fourthsemiconductor layers, wherein the first semiconductor layer has acomposition equation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), whereinthe third semiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the active layerincludes a plurality of quantum barrier layers and a plurality ofquantum well layers having a material different from the quantum barrierlayers, wherein the plurality of quantum well layers include an AlGaNbased layer, wherein the second electrode layer includes a reflectivelayer, wherein the plurality of quantum barrier layers has a larger bandgap energy than that of the quantum well layers, wherein the secondsemiconductor layer has a thickness range of 1 nm to 500 nm and has athickness thicker than that of the third semiconductor layer, andwherein the first and second semiconductor layers is an n-type layer.13. The semiconductor light emitting device according to claim 12,wherein the plurality of quantum well layers of the active layer includean InAlGaN semiconductor layer.
 14. The semiconductor light emittingdevice according to claim 13, wherein at least two of the first tofourth semiconductor layers are formed of an AlGaN based semiconductorlayer.
 15. The semiconductor light emitting device according to claim13, wherein the first to fourth semiconductor layers and the pluralityof quantum barrier layers are formed of an AlGaN based layer.
 16. Thesemiconductor light emitting device according to claim 15, wherein acycle of the quantum barrier layer and the quantum well layer includes acycle of 2 to 10, and wherein each of the plurality of quantum welllayers has a thickness of more than 15 Å and each of the plurality ofquantum barrier layers has a thickness of more than 50 Å.
 17. Asemiconductor light emitting device, comprising: a first semiconductorlayer including an n-type dopant; a second semiconductor layer includingthe n-type dopant on the first semiconductor layer; an active layer onthe second semiconductor layer, wherein the active layer includes aplurality of quantum barrier layers and a plurality of quantum welllayers; a third semiconductor layer including a p-type dopant on theactive layer; a fourth semiconductor layer including the p-type dopanton the third semiconductor layer, a first electrode layer electricallyconnected to at least one of the first and second semiconductor layers;and a second electrode layer electrically connected to at least one ofthe third and fourth semiconductor layers, wherein the firstsemiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the third semiconductorlayer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the active layerincludes a plurality of quantum barrier layers and a plurality ofquantum well layers having a material different from the quantum barrierlayers, wherein the plurality of quantum well layers include an AlGaNbased layer, wherein the second electrode layer includes a reflectivelayer, wherein the plurality of quantum barrier layers has a larger bandgap energy than that of the quantum well layers, wherein the secondsemiconductor layer has a thickness range of 1 nm to 500 nm and has athickness thicker than that of the third semiconductor layer, whereinthe first and second semiconductor layers is an n-type layer, andwherein the active layer emits light of ultraviolet wavelength.
 18. Asemiconductor light emitting device, comprising: a first semiconductorlayer; a second semiconductor layer on the first semiconductor layer; anactive layer on the second semiconductor layer; a third semiconductorlayer on the active layer; a fourth semiconductor layer on the thirdsemiconductor layer; a first electrode layer connected to the firstsemiconductor layer; and a second electrode layer connected to thefourth semiconductor layer; wherein the first semiconductor layer has acomposition equation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), whereinthe third semiconductor layer has a composition equation ofAl_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0≦X,Y≦1), wherein the active layerincludes a plurality of quantum barrier layers and a plurality ofquantum well layers having a material different from the quantum barrierlayers, wherein the plurality of quantum well layers include an AlGaNbased semiconductor layer, wherein the plurality of quantum barrierlayers has a larger band gap energy than that of the quantum welllayers, wherein the second semiconductor layer has a thickness range of1 nm to 500 nm and has a thickness thicker than that of the thirdsemiconductor layer, and wherein the second semiconductor layer has acomposition equation of Al_(Y)(Ga_(x)In_(1-x))_(1-Y)N(0<Y<0.25, 0≦X≦1).19. The semiconductor light emitting device according to claim 18,wherein the first and second semiconductor layers are formed in ann-type semiconductor layer.
 20. The semiconductor light emitting deviceaccording to claim 19, wherein the first semiconductor layer has athickness thicker than that of the fourth semiconductor layer and thethird semiconductor layer has a thickness thinner than that of thefourth semiconductor layer.